CONCRETE MIXING RATIOS

When making concrete it's important to use the correct concrete mixing ratios to produce a strong, durable concrete mix.

To make concrete there are four basic materials you need: portland
cement, sand, aggregate (stone), and water. The ratio of aggregate to
sand to cement is an important factor in determining the compressive
strength of the concrete mixture.

A concrete mixture ratio of 1 part cement, 3 parts sand, and 3 parts
aggregate will produce a concrete mix of approximately 3000 psi.

Mixing water with the cement, sand, and stone will form a paste
that will bind the materials together until the mix hardens. The
strength properties of the concrete are inversely proportional to the
water/cement ratio.

Basically this means the more water you use to mix the concrete
(very fluid) the weaker the concrete mix. The less water you use to mix
the concrete (somewhat dry but workable) the stronger the concrete mix.

Accurate concrete mixing ratios can be achieved by measuring the
dry materials using buckets or some other kind of measuring device. By
measuring the mixing ratios you will have a consistent concrete mix
throughout your entire project.

This
mixing ratio will give you a concrete mix that is strong, durable, and
good for most concrete projects. A cubic yard of concrete will fill an
area 8 feet wide by 10 feet long by 4 inches thick, or 80 square feet @ 4
inches thick.

At 6 inches thick a cubic yard of concrete will
fill an area 52 square feet and at 5 inches thick, it will fill an area
that's 65 square feet.

To produce a cubic yard of 4000 psi concrete, you have to adjust the concrete mixing ratio to:

1. 611 pounds of cement or (277kg)

2. 1450 pounds of sand or (657kg)

3. 1600 pounds of stone or (725kg)

4. 33- 35 gallons of water or (133L)

As you can see a little more cement and a little less sand is
required to produce this stronger concrete mix that is great for
driveways, pool decks, sidewalks, exterior patios, and commercial
garages.

Knowing the weight of the materials and how much water to use
should help you determine how much cement, sand, and stone to purchase
to complete your project.

For estimating purposes, you can make about 1 cubic yard of
concrete with 5 1/2 94-pound bags of cement, 17 cubic feet of sand, and
18 cubic feet of gravel. (It takes about forty 80-pound bags of
prepackaged materials to make 1 cubic yard of concrete.)

Or 1 cubic meter of concrete will require approximately 7.15 bags of Portland cement, .48 cubic meters of sand, and .51 cubic meters of gravel.

If you need less than 1 cubic yard of concrete (or if ready-mix is
not available) you can mix your own on site either by hand or using a
concrete mixer like the one pictured above.

To make smaller batches of concrete, use the same
proportions, but with smaller quantities, substituting buckets for
cubic feet. (For the mix proportions given previously, you'd use 1
bucket of cement, 3 buckets of sand, 3 buckets of stone, and 1/2 bucket
of water.)

For any batch size, the most important thing is to keep the
proportions of the ingredients the same. You can double or triple the
batch size simply by doubling or tripling the number of buckets of each
ingredient you add to the mix.

For very small projects, such as setting a mailbox post or doing
repairs, you may want to purchase a packaged concrete mix. Such a mix
combines cement, sand, and gravel in the correct mixing ratios and
requires only the addition of water to create fresh concrete.

These concrete mixture ratios are designed for the concrete to
reach full strength at or around 28 days. Curing the concrete can be
done by keeping it wet after the first day until the concrete is 7 days
old. This is an important step to take for the concrete to achieve full
strength by 28 days.